Double-layer sliding bearing

ABSTRACT

A double-layer sliding bearing comprises an inner layer and an outer layer. An inner periphery of the outer layer is integrated with an outer periphery of the inner layer through moulds for molding processes. A circular bearing surface is formed on either an inner periphery of the inner layer or an outer periphery of the outer layer. A layer having the bearing surface is arranged by a porous thin-wall layer with high forming density. The other layer not having the bearing surface is arranged by a porous thick-wall layer with low forming density.

FIELD OF THE INVENTION

The invention relates to sliding bearing techniques, particularly to a bearing of radially integrated two layers with notable differences in density and porosity for improving performance under severe operating conditions.

BACKGROUND OF THE INVENTION

Various types of sliding hearings possessing self-lubricating feature have been developed; one of the important types being those made from a uniform porous structure via compacted and sintered metals formed by a technique known as powder metallurgy. In such sliding bearings to achieve a high porosity cannot balance a high density need for overall structural robustness and wear resistance of a bearing surface which is referred to a sliding surface for bearing relative rotation. In contrast, to achieve the high density cannot balance the high porosity need for sufficient lubricating media content. Hence to apply those to severe operating conditions, such as shaft rotating at high speed, heavy load and strong vibration, especially when contact pressure and velocity (PV) limit larger than 500 MPa·m/min will be subject to stern challenges. The lubricating media means lubricating oil and lubricant having a higher viscosity than the lubricating oil.

SUMMARY OF THE INVENTION

The double-layer sliding bearing includes a high porosity thick-wall layer being radially integrated with a high density thin-wall layer.

The invention of the double-layer sliding bearing can notably provide many advantages, such as:

The invention provides a thick-wall layer with high porosity to impregnate sufficient lubricating media and prolong the service life.

The invention provides a thin-wall layer with high density to enhance wear resistance and anti-fatigue friction of the bearing surface.

The invention provides at least one groove axially indented on the bearing surface of the inner layer to accommodate debris or oxides.

The invention provides a molding process for a reinforced thin-wall layer to optimize density uniformity and enhance structural strength.

The invention provides a molding process for a reinforced and perforated thin-wall layer to smooth to of the lubricating media.

The invention provides a molding process for the bearing to integrally limn a prepared thin-wall layer with a powder forming the thick-wall layer.

The invention provides a novel sliding hearing with good lubricity, robustness and anti-abrasion to apply to the severe operating conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exploded view of a first embodiment of a double-layer sliding bearing.

FIG. 2 is a schematic of a molding process for the double-layer sliding bearing before compaction.

FIG. 3 is a schematic of the molding process illustrated in FIG. 2 to compress the filled powder via an upper punch.

FIG. 4 is a schematic of the molding process illustrated in FIG. 3 to house a dummy part within the upper punch.

FIG. 5 is a schematic of the molding process illustrated in FIG. 4 to take the bearing out of a cavity.

FIG. 6 is an exploded view of a second embodiment of a double-layer sliding bearing.

FIG. 7 is a schematic of a molding process for the double-layer sliding bearing before compaction.

FIG. 8 is a schematic of a third embodiment or a molding process for a double-layer sliding bearing before compaction.

FIG. 9 is a schematic of a fourth embodiment of a molding process for a double-layer sliding bearing before compaction.

FIG. 10 is a schematic of a fifth embodiment to form a reinforced high density thin-wall layer.

FIG. 11 is a schematic of a sixth embodiment to form a reinforced and perforated high density thin-wall layer.

DETAILED DESCRIPTION

FIGS. 1-5 are a first embodiment of a double-layer sliding bearing 1 including an inner layer 10 and an outer layer 20. An inner periphery of the outer layer 20 is integrated with an outer periphery of the inner layer 10 through moulds for molding processes. The inner layer 10 is arranged by a porous thin-wall with high forming density and may contain a certain amount of anti-abrasion element. The outer layer 20 is arranged by a porous thick-wall with low forming density (i.e. high porosity) and may contain a small amount of the element. The shape and size of the inner periphery of the outer layer 20 match with that of the outer periphery of the inner layer 10 adapted to be press-fitted with each other tightly. A circular bearing surface 10A forming an axial hole 12 for bearing a rotatable shaft (not shown) is formed on an inner periphery of the inner layer 10. A mounting surface 20B for the installation of the bearing 1 is formed on an outer periphery of the outer layer 20. Thus the double-layer sliding bearing 1 has significant radial differences in density and porosity, and excellent wear resistance on the bearing surface 10A.

The outer periphery of the inner layer 10 sets at least one rib 15 formed axially thereon to latch on the corresponding at least one slot 25 formed on the inner periphery of the outer layer 20 to enhance structural robustness, anti-vibration capability and load capacity. Similarly, the rib 15 may also be formed on the inner periphery of the outer layer 20 to latch on the corresponding slot 25 formed on the outer periphery of the inner layer 10.

Further, the double-layer sliding bearing 1 includes at least one groove 18 axially indented on the bearing surface 104 of the inner layer 10. Through the rotation of the shaft, the surplus lubricating media on the bearing surface 10A can be introduced into the groove 18 to reduce the loss of lubricating media and prevent the internal pollution of motor. In addition, the fine debris or oxides on the bearing surface 10A can also be introduced into the groove 18 to reduce tribology friction and avoid wear damage.

FIGS. 2-5 provide a molding process to form the double-layer sliding bearing 1 via a prepared high density thin-wall inner layer 10 to simplify the fabrication in mass production. The mould for the molding process includes a central core rod 30 surrounded by a die 32, between which an upper punch 34 and a lower punch 36 can apply compaction forces separately. A cavity 31 of the mould is a concaved space with an elevation not higher than a die surface 33 and is formed by surrounding the core rod 30 and the die 32 and the upper punch 34 and the lower punch 36, all of which can be positioned, moved up and down separately.

Referring to FIG. 2, after loading the prepared thin-wall inner layer 10 in the cavity 31 to respectively make its lower end face and the bearing surface 10A in contact with the corresponding lower punch 36 and axial periphery of the core rod 30, a dummy part 38 having a same diameter of the bearing surface 10A and a same thickness of the inner layer 10 is loaded in the cavity 31 in contact with the inner layer 10 and with its upper end face aligning to the die surface 33. Then a powder 22 forming the thick-wall outer layer 20 is filled in a remaining space of the cavity 31.

Referring to FIG. 3, the descending upper punch 34 further applies a compaction force on the powder 22 until an end face of the upper punch 34 aligns to an upper end face of the inner layer 10, thereby forming the double-layer sliding bearing 1 in the cavity 31.

Referring to FIG. 4, the dummy part 38 is housed in the upper punch 34 and the upper punch 34 is ascended away from the die surface 33.

Referring to FIG. 5, the ascending lower punch 36 pushes the bearing 1 until an end face of the lower punch 36 aligns to the die surface 33, thereby taking the double-layer sliding bearing 1 out of the cavity 31.

FIG. 6 is a second embodiment of a, double-layer sliding bearing 1 a including an inner layer 10 and an outer layer 20. This differs from the first embodiment shown in FIG. 1 mainly in that the outer layer 20 having a bearing surface 20A on the outer periphery is arranged by a porous thin-wall with high forming density, and the inner layer 10 having a mounting surface 10B on the inner periphery is arranged by a porous thick-wall with low forming density. The rib 15, the slot 25, and the groove 18 arranged in the first embodiment are omitted to simplify the illustration.

FIG. 7 provides a molding process before compaction, similar to the first embodiment shown in FIG. 2, to form the double-layer sliding bearing 1 a. After loading the prepared outer layer 20 in the cavity 31 to respectively make its lower end face and the bearing surface 20A in contact with the corresponding lower punch 36 and axial periphery of the die 32, a dummy part 38 having a same diameter of the bearing surface 20A and a same thickness of the outer layer 20 is loaded in the cavity 31 in contact with the outer layer 20 and with its upper end face aligning to the die surface 33. Then a powder 22 forming the inner layer 10 is filled in a remaining space of the cavity 31. Thus the bearing 1 a can be formed by the same subsequent modeling process illustrated in the first embodiment.

The inner layer 10 and the outer layer 20 of the double-layer sliding bearing 1, 1 a can be made respectively by a blending powder 22 from a commonly used base element such as at least one of Fe, Cu and C powder 22 and the anti-abrasion element such as at least one of Ni, Cr, Mo and Mn powder 22. In fact, the thin-wall layer with high forming density may have a considerable degree of structural strength and abrasion resistance, so that the inner layer 10 and the outer layer 20 can also be made from the base element only. The Fe powder 22 includes at least one of pure Fe powder 22 and Cu coated Fe powder 22. The Cu in the Cu powder 22 and Cu coated Fe powder 22 includes at least one of copper, brass and bronze.

FIG. 8 is a third embodiment to illustrate a simplified molding process before compaction to form the double-layer sliding bearing 1 without the use of the dummy part 38 via a mould slightly modified from the mould. The mould has an annular groove 30 a formed by axially indenting from a top of the core rod 30 to fit just right for accommodating the thin-wall inner layer 10 therein. After loading the prepared inner layer 10 in the annular groove 30 a, a powder 22 forming the outer layer 20 is filled in a remaining space of the cavity 31 with an axial length of the powder 22 longer than that of the inner layer 10. The subsequent modeling processes (not shown) include that the upper punch 34 with its end lace covering an upper area of the cavity 31 abuts on the die surface 33, and the ascending lower punch 36 further applies a compaction force on the powder 22 until an end face of the lower punch 36 aligns to a lower end lace of the inner layer 10, thereby forming the bearing 1 in the cavity 31. After ascending the upper punch 34 away from the die surface 33, the die 32 and the core rod 30 are simultaneously descended to take the bearing 1 out of the cavity 31.

FIG. 9 is a fourth embodiment, similar to the third embodiment shown in FIG. 8, to illustrate a simplified molding process before compaction to form the double-layer sliding bearing 1 a. The mould has an annular groove 32 a formed by axially indenting from a top of the die 32 to fit just right for accommodating the high density thin-wall outer layer 20 therein. After loading the prepared outer layer 20 in the annular groove 32 a, a powder 22 forming the low density inner layer 10 is filled in a remaining space of the cavity 31 with an axial length of the powder 22 longer than that of the outer layer 20. Thus the double-layer sliding bearing 1 a can be formed by the same subsequent molding process illustrated in the third embodiment.

The invention can be widely applied to different devices; the position and form for the installation of the double-layer sliding bearing 1, 1 a are not limited to the drawings shown in the mounting surface 20B, 10B; and also the inner layer 10 and the outer layer 20 need not be limited to the same length. To meet such application requirements, a similar modeling process for the bearing can be realized by modifications or adjustments of the embodiments of the invention via the disclosed technical means and features, such as dimensions of the relevant mould components, configuration of the cavity 31, number and length of the dummy part 38 (if necessary), filling position of the powder 22, compressing length and position of the upper punch 34 and the lower punch 36, which do not depart from the spirit and scope of the invention.

FIG. 10 is a fifth embodiment to firm a reinforced high density thin-wall layer of the double-layer sliding bearing 1 (or 1 a). In practical, there is a dilemma in forming the high density thin-wall layer that it too thin will cause poor filling property of the powder 22, seriously affecting uniformity of high density compaction; instead, it too thick will raise material cost due to increase the use of anti-abrasion or Cu element. The technical means for solving the dilemma is provided as follow. First of all, at least two short thin-wall layers 10 a, 10 b (or 20 a, 20 b) are respectively formed by pressing the powder 22 forming the thin-wall layer in the cavity 31 via at least one of the upper punch 34 and the lower punch 36. Only two short thin-wall layers 10 a, 10 b (or 20 a, 20 b) are schematically shown in FIG. 10 to simplify the illustration. Each short thin-wall layer 10 a, 10 b (or 20 a, 20 b) has a same diameter of the bearing surface 10A (or 20A) and as same thickness of the thin-wall layer. A total length of at least two axial abutting short thin-wall layers 10 a, 10 b (or 20 a, 20 b) is longer than a length of the thin-wall layer causing a forming density of each short thin-wall layer 10 a, 10 b (or 20 a, 20 b) lower than that of the thin-wall layer. Then the at least two axial abutting short thin-wall layers 10 a, 10 b (or 20 a, 20 b) are loaded in the cavity 31 and pressed at least once via the at least one of the upper punch 34 and the lower punch 36 until the total length of the at least two axial abutting short thin-wall layers 10 a, 10 b (or 20 a, 20 b) is equal to the length of the thin-wall layer.

FIG. 11 is a sixth embodiment to form a reinforced and perforated high density thin-wall layer of the double-layer sliding bearing 1 (or 1 a). This differs from the fifth embodiment mainly in that plural penetrating notches 39 are radially indented on at least one of two adjacent end faces between at least one pair of two adjacent short thin-wall layers 10 a, 10 b (or 20 a, 20 b) of the at least two axial abutting short thin-wall layers 10 a, 10 b (or 20 a, 20 b). The reinforced and perforated high density thin-wall layer not only enhances structural robustness of the double-layer sliding bearing 1 (or 1 a) and wear resistance of the bearing surface 10A (or 20A), but also ensures smooth transmission of the lubricating media enriched in the high porosity thick-wall layer to the bearing surface 10A (or 20A), thereby significantly improving the PV limit of the double-layer sliding bearing 1 (or 1 a) for long-term operation under the severe operating conditions.

While the preferred embodiments of the invention have been set forth for the purpose of disclosure, they are not the limitations of the invention, modifications of the disclosed embodiments of the invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the invention. 

What is claimed is:
 1. A double-layer sliding bearing, comprising: an inner layer and an outer layer, an inner periphery of the outer layer being integrated with an outer periphery of the inner layer through moulds for molding processes, a circular bearing surface being formed on either an inner periphery of the inner layer or an outer periphery of the outer layer; wherein a layer having the bearing surface is arranged by a porous thin-wall layer with high forming density, the other layer not having the bearing surface being arranged by a porous thick-wall layer with low forming density.
 2. The double-layer sliding bearing of claim 1, wherein the shape and size of the inner periphery of the outer layer match with that of the outer periphery of the inner layer adapted to be press-fitted with each other tightly.
 3. The double-layer sliding bearing of claim 2, wherein the outer periphery of the inner layer sets at least one rib formed axially thereon to latch on the corresponding at least one slot formed on the inner periphery of the outer layer.
 4. The double-layer sliding bearing of claim 2, wherein the outer periphery of the inner layer sets at least one slot formed axially thereon to latch on the corresponding at least one rib formed on the inner periphery of the outer layer.
 5. The double-layer sliding bearing of claim 1, wherein at least one of the inner layer and the outer layer is made from at least one of Fe, Cu and C powder, the Fe powder includes at least one of pure Fe powder and Cu coated Fe powder, the Cu in the Cu powder and Cu coated Fe powder includes at least one of copper, brass and bronze.
 6. The double-layer sliding bearing of claim 1, wherein at least one of the inner layer and the outer layer contains at least one of Ni, Cr, Mo and Mn powder.
 7. The double-layer sliding bearing of claim 1, wherein at least one of the inner layer and the outer layer is made from a blending powder of at least one of Fe, Cu and C powder and at least one of Ni, Cr, Mo and Mn powder, the Fe powder includes at least one of pure Fe powder and Cu coated Fe powder, the Cu in the Cu powder and Cu coated Fe powder includes at least one of copper, brass and bronze.
 8. The double-layer sliding bearing of claim 1, wherein at least one groove is axially indented on the bearing surface of the inner layer.
 9. The double-layer sliding bearing of claim 1, wherein the mould includes a central core rod surrounded by a die, between which an upper punch and a lower punch can apply compaction forces separately, a cavity of the mould is a concaved space with an elevation not higher than a die surface and is formed by surrounding the core rod and the die and the upper punch and the lower punch, all of which can be positioned, moved up and down separately.
 10. The double-layer sliding bearing of claim 9, wherein at least two short thin-wall layers are respectively formed by pressing a powder forming the high density thin-wall layer in the cavity via at least one of the upper punch and the lower punch, each short thin-wall layer has a same diameter of the bearing surface and a same thickness of the thin-wall layer, a total length of at least two axial abutting short thin-wall layers is longer than a length of the thin-wall layer causing a forming density of each short thin-wall layer lower than that of the thin-wall layer, then the at least two axial abutting short thin-wall layers are loaded in the cavity and pressed at least once via the at least one of the upper punch and the lower punch until the total length of the at least two axial abutting short thin-wall layers is equal to the length of the thin-wall layer.
 11. The double-layer sliding bearing of claim 10, wherein plural penetrating notches are radially indented on at least one of two adjacent end faces between at least one pair of two adjacent short thin-wall layers of the at least two axial abutting short thin-wall layers.
 12. The double-layer sliding bearing of claim 9, wherein after loading the prepared high density thin-wall layer in the cavity to respectively make its lower end face and the bearing surface in contact with the corresponding lower punch and axial periphery of either the core rod or the die, a dummy part having a same diameter of the bearing surface and a same thickness of the thin-wall layer is loaded in the cavity in contact with the thin-wall layer and with its upper end face aligning to the die surface, then a powder forming the low density thick-wall layer is filled in a remaining space of the cavity, and then the descending upper punch applies a compaction force on the powder until an end face of the upper punch aligns to an upper end face of the thin-wall layer.
 13. The double-layer sliding bearing of claim 9, wherein the mould has an annular groove formed by axially indenting from a top of either the core rod or the die to fit just right for accommodating the thin-wall layer therein.
 14. The double-layer sliding bearing of claim 13, wherein after loading the prepared high density thin-wall layer in the annular groove, a powder forming the low density thick-wall layer is filled in a remaining space of the cavity with an axial length of the powder longer than that of the thin-wall layer, then the upper punch with its end face covering an upper area of the cavity abuts on the die surface, and then the ascending lower punch applies a compaction force on the powder until an end face of the lower punch aligns to a lower end face of the thin-wall layer. 